IS77.1 171 



It may be conjectured tliat beiieatli pure Italian skies the portion 

 of the year passed by the Vnnessidcs in hibernation would be brief ; 

 but in more northern countries the few species that gladden the 

 landscape shrink from encountering the first visits of the benumbing 

 airs of winter. I took advantage of a singular opportunity thus 

 afforded, during a sojourn in the Highlands, to investigate the capa- 

 bility of V. urtic<e for stridulation. On the 22nd of August, a dull 

 day, when there had been a sudden fall in the temperature, a fresh 

 brood of the Tortoiseshell-butterflies, newly sunning themselves at 

 West Loch Tai'bert, hastened from the fields to shelter aud remain 

 torjjid, perchance to dream. I detached one of these, a female, 

 hanging on cobwebs in an outhouse, and seated her, still drowsy, on 

 the palm of my hand. Then with the other hand, touching lightly the 

 tails of the hind-wings, I induced her to depress and shut the wings 

 successively. Each time she testily performed this action I heard 

 distinctly, as the fore-wings were brought forward, ivhen only the 

 extreme hasal portion of the ivings were in contact, a soft sound, like 

 gratinrj sand-paper. 



In V. urticce then certainly, and in V. lo more than probably, it 

 will be noticed, the sound produced by the vexed insect must have 

 arisen from the friction of some hard parts at the basal portion of the 

 wings ; and if so, it had long struck me the analogy of the stj-idulation 

 of the leaf-crickets would point to the possession of some chitinous 

 serrature or file, situated on one of the veins, which would also account 

 for the stridor having so distinct a sound-colour of sand-paper. 

 Prepossessed with this idea, I submitted specimens of the wings of 

 V. urticce and of V. lo, male and female, to an excellent microscope of 

 several working degrees of power that I had borrowed expressly for 

 the purpose, and I then found, whenever the under surface of a 

 fore-wing of either insect was focussed and adjusted, the required file 

 or sei'rature (lima) came at once to view, situated on the anal vein at 

 its base, and running along it for one-third of its length, for which 

 distance it is tumid, spindle-shaped, and bare of scales. In the case 

 of lo, and I believe also of urticce, it was much more strongly developed 

 in the female than the male, and the vein had a blacker, firmer consis- 

 tence. In structure, this lima did not much differ from that which we 

 find in a musical cricket or Icaf-crickct (formed, as I have reason to 

 believe, by an unusual development, which metamorphoses the various 

 ])arts of the wing and protrudes the spiral thread that surrounds the 

 hollow wing-veins as well as the tracheae), but the teeth were somewhat 

 less regular. 



